This invention relates to a contact assembly for a circuit breaker. More particularly, this invention relates to the primary disconnect assemblies which electrically couple a circuit breaker to a bus bar assembly.
Normally, industrial circuit breakers are coupled to the circuit they are protecting by primary disconnect assemblies. FIGS. 5, 6, 7, and 9 of U.S. Pat. No. 4,218,596 illustrate the general type of primary disconnect assemblies with which the present invention is concerned. The figures of U.S. Pat. No. 3,641,300 also illustrate this type of primary disconnect assembly. Referring to FIG. 2 of U.S. Pat. No. 3,641,300, this figure illustrates a primary disconnect assembly which is mounted on an electrically conductive circuit breaker stud and which is shown in engagement with an electrically conductive bus bar stud (terminal).
A disadvantage of the primary disconnect assemblies of U.S. Pat. Nos. 4,218,596 and 3,641,300 is that they provide only one current carrying contact location between each contact finger and its associated bus bar terminal. Additionally, this arrangement provides little restraining force to resist the separation of the primary disconnects or their movement relative to the circuit bus bars during short circuit conditions. In the prior art, friction between the contact fingers and the bus bar terminals is the only force present to prevent the fingers from moving relative to the terminals. In some situations friction is not enough to prevent the fingers from moving relative to the terminals. For example, under certain load conditions when a circuit breaker interrupts a current flow, the circuit breaker can subject the fingers to forces which tend to slide the fingers along the terminals.